Conventionally, easily formed plastic containers are often used for packaging and distributing foods and drinks or the like. Recently, however, paper containers have been reconsidered in view of various environmental problems encountered with the use of plastics such as outflow of environmental toxins, difficulty of plastic waste treatment after use, and the like. With regards to methods for manufacturing a paper container, there are well-known pasting and paper making methods. In one such conventional pasting method, for example, paper which has been subjected to a laminating process is used, two sheets of such paper each forming a barrel portion and a bottom portion of a container, respectively, and thereafter both sheets are subjected to adhesion with pressure and heat in a mold or other processing to be adhered and integrated together to form a container.
In another paper container making method, paper fibers are dispersed in water, the colloid solution thus obtained is filtered by a paper making net, paper material remaining on the paper making net is dehydrated to thereby make a prototype of a container, and thereafter the prototype of the container is hot air dried or heat pressed. In this method, however, there are drawbacks in that it is not only necessary to increase the number of steps and thus cost of manufacturing over the above pasting method, but also a container obtained by this method is weakened by water so that it cannot be used for a product requiring waterproofing such as a drink container or flowerpot.
For these reasons, there has conventionally been known a widely utilized drawing method for integrally forming a paper container integrally from a sheet of blank paper. According to this drawing method, containers having waterproof properties can be efficiently manufactured by using blank paper which has been subjected to lamination processing.
Since this type of paper container is formed integrally of a single sheet of blank paper, it can be relatively easily manufactured with a reduced number of steps. However, there are disadvantages in that setting conditions at the time of working are very severe. In particular, when the blank paper is subjected to deep drawing, the blank is injured. Accordingly, a conventional paper container obtained by the above drawing method has a shallow bottom and application thereof is restricted.